Direct burner ignition system

ABSTRACT

A direction ignition system is provided for a valve controlled ignition system. The system utilizes an electrically actuated electromagnetic valve means connected between the fuel burner and a fuel supply. The valve means has an armature and includes means for biasing the armature in a normally closed position. The biasing means is adjustable and force-calibrated to prevent actuation of the valve means at less than a minimum voltage drop thereacross. The system also includes a fuel ignition element, electrically in series with the electromagnetic valve means, which reaches fuel ignition temperature in response to a predetermined current flow. Alternatively, there may be provided an electrically actuated thermal valve, fluidically in series with the electromagnetic valve means, and electrically in series with the fuel ignition element. The electromagnetic valve means is then in parallel electrically with the thermal valve and ignition element.

United States Patent [191 Hantack 1 1 Jan. 28, 1975 DIRECT BURNERIGNITION SYSTEM [75] Inventor: Melvin E. Hantaclt, St. Louis, Mo.

[73] Assignee: Eaton Corporation, Cleveland, Ohio [22] Filed: Jan. 16,1974 [21] Appl. No.: 433,939

Related U.S. Application Data [63] Continuation-impart of Ser. No.281,067, Aug. 16,

Primary Examiner-Edward G. Favors Attorney, Agent, or Firm-Teagno &Toddy [57] ABSTRACT A direction ignition system is provided for a valvelcontrolled ignition system. The system utilizes an electricallyactuated electromagnetic valve means connected between the fuel burnerand a fuel supply. The valve means has an armature and includes meansfor biasing the armature in a normally closed position. The biasingmeans is adjustable and force-calibrated to prevent actuation of thevalve means at less than a minimum voltage drop thereacross. The systemalso includes a fuel ignition element, electrically in series with theelectromagnetic valve means, which reaches fuel ignition temperature inresponse to a predetermined current flow. Alternatively, there may beprovided an electrically actuated thermal valve, fluidically in serieswith the electromagnetic valve means, and electrically in series withthe fuel ignition element. The electromagnetic valve means is then inparallel electrically with the thermal valve and ignition element.

13 Claims, 7 Drawing Figures /Z0 VAC PATENTEB JAN 2 8 IQYS SHEET 10F 3FIG. I

FIG. 2

DIRECT BURNER IGNITION SYSTEM This application is a continuation-in-partof my copending application Ser. No. 281,067, filed Aug. 16, 1972.

BACKGROUND OF THE INVENTION This invention relates generally to fuelignition systems for valve controlled burners and particularly to directignition systems using an igniter element which allows an increasedcurrent flow to actuate a valve upon reaching an ignition temperature.

Prior art burner ignition devices generally fall into two categories,namely, indirect and direct ignition devices.

The indirect ignition devices generally comprise pilot flame ignitedburner systems wherein a fluid filled thermoresponsive device iscontinuously heated by the pilot flame to a predetermined temperature atwhich the expanded fluid of the thermocouple allows the main valve to beopened to provide fuel flow to the burner which is then ignited by thepilot flame. One drawback of such devices is that the positioning of thethermocouple to the pilot flame is quite critical. Improper placement ofthe thermocouple either too far from the flame or too near to the coldpart of the flame will not heat the thermocouple sufficiently to openthe mairi valve. Another drawback is that the pilot flame may be shiftedfrom the thermocouple by an air draft or completely extinguished therebypreventing the main valve from opening in either case. Because the pilotflame is burning continuously, a waste of fuel results during any periodof time when the main burner is not actuated. The waste is especiallygreat during relatively mild parts of the winter when heat is neededonly periodically, but the pilot flame burns constantly.

Direct ignition systems are known which utilize electrical means forproducing sparks to directly ignite fuel flowing from a burner. A timingcircuit is used in conjunction with the spark ignition means toterminate fuel flow to the burner if the fuel is not ignited within apredetermined time. Some flame detection means are also required forindicating to the timing circuit whether the fuel has been ignited ornot. As such these systems are complicated and expensive and requireextensive troubleshooting to determine the cause of any failureoccurring therein.

Direct ignition systems are also known which utilize a glow coil orheater element which is heated to the fuel ignition temperature andwhich are operable to ignite the fuel flowing from the burner. In thesesystems, some type of flame detecting means is required to terminatefuel flow should the heater element fail to ignite the fuel. Thedetecting means may comprise infra-red sensors or flame conductivitysensors along with their associated circuitry. Such a system isdisclosed in [1.8. Pat. No. 3,649,156 issued to Leonard E. Conner. Itwill be appreciated that such a system requiring separate flame ignitingand flame sensing elements is complicated and expensive since extensivecircuitry is required to coordinate the igniting and sensing functionsinto an operative system.

SUMMARY OF THE INVENTION The present invention provides a new andimproved direct burner ignition system which is simple in constructionand inexpensive to manufacture and operate.

The system requires no separate flame sensing means to maintainoperation since it is capable of providing electrical failsafeoperation.

In one embodiment of the invention a variable resistance means providesa first resistance value when at ambient temperature and a secondresistance value when heated by connection to an electrical powersource. Valve actuating means are electrically series connected to thisvariable resistance means and are operable to allow fuel to flow to aburner only after the variable resistance means achieves the secondresistance value.

In another embodiment of the invention an electromagnetic valve isconnected between a fuel supply and a burner to provide a flow of fuelto the burner in response to a predetermined current. Ignition means,having a resistance which decreases with increased temperature ismounted proximate to the burner to provide an element which attains theignition temperature of the fuel in response to the same predeterminedcurrent. Series circuit means connect the valve and the ignition meansto a power source whereby current flow from the power source isoperable: to increase the temperature of the ignition means therebydecreasing the resistance of the series circuit and allowing thepredetermined current value to be obtained in the circuit.

In yet another embodiment of the invention a parallel electric circuitmeans is series connected with the ignition means to control a heatvalve and an electromagnetic valve in response to the ignition meansattaining fuel ignition temperature. The electromagnetic valve has anarmature and includes means for biasing the armature in a normallyclosed position. The biasing means is adjustable to prevent actuation ofthe valve at less than a minimum voltage drop across the electromagneticvalve.

The series connection of the temperature ignition means with the valveor valves which control fuel flow to the burner in the above describedembodiments provides a simple and inexpensive direct fuel ignition apparatus which assures that fuel flow will occur only when the ignitionelement is at the fuel ignition temperature. Therefore, there is norequirement for any separate flame sensing devices or delay circuitry asthe present invention automatically provides electrical fail-safeoperation.

It is, therefore, an object of this invention to provide a simple andinexpensive direct ignition system which is electrically fail-safe.

It is a more specific object of the present invention to provide asystem which insures that no fuel can flow when the ignition element isbelow the ignition temperature, even under extreme circumstances, suchas a low voltage condition.

Another object of this invention. is to provide a fuel valve actuatingsystem which is operable to actuate a fuel valve in response to apredetermined resistance of a variable resistance means which iselectrically connected to the fuel valve.

Another object of this invention is to provide a direct ignition systemwhich allows fuel flow to a burner only upon an ignition elementattaining a fuel ignition temperature.

Another object of the invention is to provide a direct fuel ignitionsystem which is operable to actuate a plurality of valves to providefuel flow to a burner in response to an ignition element attaining afuel ignition temperature.

These and other objects of the invention will become more apparent fromthe description of the drawings and the detailed description of thepreferred embodiment, which follows hereinafter.

BREIF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing of oneseries connected direct ignition system.

FIG. 2 is a schematic drawing of a series-parallel connected directignition system.

FIG. 3 is a sectional side view of a thermally actuated bimetal valvewhich may be used in conjunction with the circuit of FIG. 2.

FIG. 4 is a top view of the bimetal portion of the thermally actuatedvalve of FIG. 3.

FIG. 5 is a graph of resistance of, and current flow through the igniterelement versus temperature of the igniter element.

FIG. 6 is a graph of current in the series circuit of FIG. 1 versus timeafter connection to a 120 Volt A.C.

power source.

FIG. 7 is a semi-schematic sectional side view of a calibrated solenoidvalve of the type which may be used in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawingswherein FIG. I shows a 120 Volt A.C. power source connected across apair oflines L and L with a thermostat switch 18, a coil 16, a trimresistor potentiometer 20, an igniter l4 and a fuse 22 all electricallyconnected in a series circuit associated therewith. This series circuitprovides a direct ignition system for a burner 10. Fuel flow to theburner 10 is controlled by a solenoid valve 24 positioned in a conduit26 between the burner 10 and a fuel supply.

The solenoid valve 24 is positioned to be actuated by the coil 16 as isindicated by the dotted line 25 in a manner that will be describedlater. The igniter 14 is mounted proximately to the outlet of the burner10 to allow the fuel from the burner 10 to flow directly onto theigniter 14 upon actuation of the valve 24.

The operation of the circuit of FIG. 1 is best understood with referenceto the graphs of FIGS. 5 and 6. A master control thermostat (not shown)is used to set a reference temperature to which the thermostat switch 18controls the burner flame to maintain the reference temperature setting.However, since this part of the circuit is conventional in the art itneed not be illustrated for purposes of understanding the invention. Thethermostat switch 18 closes and allows the voltage across line L L to beapplied to the series circuit connected therebetween. The resistances ofthe trim resistor 20, the fuse 22 and the coil 16 are selected to benegligible as compared to the initial resistance of the igniter.

The igniter 14 is preferably a negative slope thermistor which iscomposed of silicon carbide materials and exhibits a decreasedelectrical resistance with increased temperature. A typical resistancev. temperature curve for such an igniter is disclosed at FIG. 5. Suchigniters are readily available from the Carborundum Company of NiagaraFalls, New York.

As is seen in FIG. 5 the igniter 14 has a resistance of 240 ohms at theinitial ambient temperature of 80F. when the series circuit between L,and L is first connected to the 120 Volt A.C. power source. The initialcurrent flowing through the igniter 14 is approximately 0.45 amps andthe line voltage is proportioned therefore between the igniter andremaining elements with a 108 VAC drop across the igniter l4 and 12 VACdrop across the remaining elements. The igniter 14 is heated by thecurrent flowing therethrough and rises in temperature while exhibiting acorresponding decrease in resistance until the resistance startsleveling off, at approximately l,600F., to an approximate value of 38ohms. Of course, as the igniter l4 resistance decreases, the current inthe series circuit between L, and L increases, due to a decrease intotal circuit resistance, until it also levels out to an approximatevalue of 3 amps.

The solenoid valve 24 is preselected to allow fuel flow to the burner 10whenever a current of approximately 2.8 amps flows through the heatercoil associated therewith. Because this current flow is possible onlywhen the resistance of the igniter I4 is approximately 38 ohms and thisigniter resistance is possible only when the igniter 14 is at 2,200F. orgreater, ignition of the fuel flowing from the burner 10 is therebyassured since fuels such as natural gas have an ignition temperature ofapproximately 1,600F.

Once the fuel flowing from the burner is ignited, the burner 10 willheat the surroundings until the thermostat senses that the preselectedtemperature has been attained and will then open the switch 18 toterminate current flow and close the valve 24 preventing further fuelflow to the burner 10. The igniter 14 is also disconnected from thepower source by the switch 18 and cools down to its initial temperature.

The trim resistor 20 is a manually adjustable potentiometer by whichresistance may be added to the circuit and the maximum current flowingtherein minimized thereby. The circuit is protected by a fuse 22 whichwill open circuit in situations of excessive current flow in thecircuit.

The circuit outlined above is electrically failsafe in that anymalfunction of the component parts will not cause a hazardous conditionby allowing fuel to flow without it being ignited by the igniter 14.Should an open circuit develop in either the igniter 14 or the coil 16current flow to the solenoid valve 24 would stop and the valve 24 wouldclose to shut off fuel flow to the burner. If a short circuit developsin the igniter 14, the fuse 22 would open the circuit due to excessivecurrent flow and prevent current flow to the valve 24 shutting off fuelflow. If the'coil 16 is short circuited, current flow therein would stopand the valve 24 would shut off fuel flow even though the igniter wason.

FIG. 7 illustrates semi-schematically a preferred form of the solenoidvalve 24 for use in the subject embodiment. The valve 24 isforce-calibrated, i.e., the biasing means which maintains the armaturein a normallyclosed position is precisely set to be overcome by apredetermined, minimum voltage drop across the solenoid valve. The valve24 includes an armature 70 positioned within an armature guide 72. Thesolenoid coil 16 is wound on a bobbin 76, which is fitted over the guide72 and the entire assembly is encased within the soleagainst armature 70is precisely controlled by a calibration means, shown herein as athreaded compressionadjusting member 86, which may be adjusted by meansof slot 88. it should be clearly understood, of course, that the biasingof the armature may be accomplished by other means, such as anaccurately calibrated biasing spring, and the important feature of thepreferred embodiment of FIG. 7 is the ability to precisely control thevoltage drop across the solenoid valve which is required to actuate thearmature, lifting the head 80 out of the seat 82 and opening supply line26'. It should also be noted that other head and seat arrangements maybe utilized and the present invention is in no way dependent upon anyparticular such arrangement.

The time within which specific circuit actions take place are seen inthe graph of FIG. v6. When the circuit is first connected to the 120 VACpower supply at time 0 seconds a current of approximately 0.45 ampsinitially flows in the circuit and rises to approximately 2.8 ampswithin the next 13 seconds. This is the minimal current which whenmaintained for a brief period of time will cause sufficient voltage (1R)drop in the coil to cause the force-calibrated solenoid valve 24 to beactuated.

Referring now to FIG. 2, wherein like parts are similarly designated,but with a prime added, the circuit shown therein is an alternativeembodiment of the direct ignition system of FIG. 1, and is particularlyadaptable to the direct ignition of burners in clothes dryerapplications. A timer switch 32 is electrically series connected with athermostat switch 18' and a dryer door actuated motor switch 30. A twobranch parallel circuit is connected between line L, and the motorswitch 30. An electromagnetic coil 16' is located on one branch and aheater coil 29 is series connected to an igniter 14' located in thesecondbranch. The electromagnetic coil 16' activates the solenoid valve24' as is indicated by dotted line 31.

Thermal valve 28 and the solenoid valve 24' are both connected in linewith the supply line 26 and fuel flow to the burner occurs only whenboth valves 24 and 28 are open.

In operation, when the timer (not shown) is set for a certain timeinterval, the timer switch 32 closes. If the thermostat (not shown)senses the dryer temperature is lower than the preselected temperaturethe thermostat switch 18 will also close. If the door is closed thedryer motor will operate and close the switch 30 to apply power to thetwo parallel branches to complete the circuit. Power applied through theheater coil 29 and igniter 14' will open the thermal valve 28 after aperiod of time when the igniter is at the fuel ignition temperature,similar to the manner which was explained previously with respect toFIG. 1. Power applied through the electromagnetic coil 16 willimmediately open the solenoid valve 24'. When the igniter 14 is at thefull ignition temperature, the valve 28 being open, fuel will flow tothe burner 10' and will be ignited by the igniter 14.

Fuel will continue to flow to the burner 10' until any one of theswitches 32,18, or 30 are opened. When either of the switches 32,18, or30 opens it stops current flow to heater coil 29 and coil 16 toimmediately shut off valve 24' to stop fuel flow. Thus when thethermostat (not shown) senses that the preselected temperature has beenattained in the dryer, the thermostat switch 18' opens and terminatescurrent flow to the solenoid coil 16' shutting off valve 29' toterminate fuel flow. When the dryer door is opened, the dryer motor (notshown) is stopped and it in turn opens the switch 30 and terminatescurrent flow to the coil 16' shutting off valve 24' to terminate fuelflow. Similarly when the timing cycle of the dryer ends, switch 32 opensand terminates current flow to the coil 16' shutting off valve 24' toterminate fuel flow.

This circuit is also electrically fail-safe because the added elementsof the coil 29 and valve 28 fail only in a non-hazardous manner. A shortcircuit of the coil 29 will prevent development of the requisite heattherein and the valve 28 will remain closed. Conversely, an open circuitof the coil 28 will prevent the requisite current flow and the valve 28will likewise remain closed.

The thermal valve 28, as shown in FIGS. 3 and 4, has an inlet 46connected to the fuel supply side of line 26. The fuel is communicatedtherethrough to a chamber 44 wherein it exerts its supply line pressureon a valve plug 50 to seal a passageway 38 extending through a seat body42 of an adjustable seat assembly 36 threaded into a valve plate 48. Anambient compensated bimetal assembly 52 is connected to the plug 50 byhaving the top portion 51 of the plug slide into a keyway formed in abimetal element 61). The bimetal 60 has one end joined to a compensatingbimetal ele' ment 58 by means known to those familiar with the art. Theother end of the element 58 is joined to an electrically insulatingterminal block 56 by means also known to those skilled in the art. Theheater coil 29 is wrapped around the element 58 with its ends connectedto electrical connecting terminals 54. The bimetal elements 58,60 arepreselected to provide a constant force on 60 as well as that of thefuel line pressure acting on the plug 50. The seat assembly 36 may beadjusted ,up or down by appropriately threading the assembly 36 in theplate 48. An adjustment slot 40 is provided to facilitate this action.When the plug 50 is lifted from the seat assembly 36 fuel flows throughthe passageway 38 into an outlet 34 which communicates with the burner10 side of the supply line 26 to supply fuel to the burner 10 thereby.

It willbe apparent to one skilled in the art that the various current,resistance and time values recited herein are merely for purposes ofillustrating the operation of one preferred embodiment of the invention,which is in no way dependent upon any particular value.

Certain modifications and improvements will become obvious to thoseskilled in the art upon reading this specification. One of such obviousmodifications and improvements would be to incorporate a flame lossoverride circuit to shut off the power to the direct ignition circuitupon loss of flame from the burner. This would function as a secondarymechanical fail-safe circuit. It is the Applicants intention, therefore,that all such obvious modifications and improvements be included withinthe scope of his invention.

Having described the invention so as to enable one skilled in the art topractice it, I claim:

1. A direct ignition system for a valve controlled fuel burnercomprising:

a. an electrically actuated thermal valve connected between said fuelburner and a fuel supply;

b. electromagnetic valve means fluidically in series I with said thermalvalve, said valve means having an armature and including means forbiasing said armature in a normally closed position, said biasing meanspreventingactuation of said valve means at less than a minimum voltagedrop across said valve means;

c. means providing a fuel ignition element proximate to the outlet ofsaid burner, said fuel ignition element reaching fuel ignitiontemperature in response to a predetermined current flow therethrough;and r d. parallel electric circuit means operating i. said thermal valvein response to a fuel ignition temperature being present in said fuelignition element, and ii. said electromagnetic valve means.

2. A direct ignition system as set forth in claim 1 wherein saidelectromagnetic valve means is a solenoid valve and said biasing meansincludes a helical compression spring.

3. A direct ignition system as set forth in claim 2 wherein said biasingmeans includes means to adjust the voltage drop required to actuate saidvalve means.

4. A direct ignition system as set forth in claim 3 wherein saidadjustment means includes an adjustable threaded member providing a seatfor said spring, said threaded member being oppositely disposed fromsaid armature.

5. A direct ignition system as set forth in claim 1 wherein said fuelignition element is a variable resis- 7. A direct ignition system as setforth in claim 1 including:

an electrical power source; and

.a manual switch series connected to said parallel circuit means tocontrol the connection of said electrical power source to said parallelcircuit means and said fuel ignition element.

8. A direct ignition system as set forth in claim 1 wherein said fuelignition element includes a negative resistance thermistor having a fuelignition temperature when a predetermined current flows therethrough.

9.. A direct ignition system as set forth in claim 1 wherein saidparallel circuit means includes a substantially constant resistanceheater mounted to said thermal valve to control the opening of saidthermal valve in response to said predetermined current flowing throughsaid resistance heater.

10. A system for igniting a fuel burner comprising:

a. electromagnetic valve means connected between said fuel burner and afuel supply, said valve means including an armature selectively movablebetween a position opening said valve means and a position closing saidvalve means, said valve means further including means for biasing saidarmature to prevent opening of said valve means at less than a minimumvoltage drop across said valve means;

b. means providing a fuel ignition element proximate to the outlet ofsaid burner, said fuel ignition element reaching fuel ignitiontemperature in response to a predetermined current flow therethrough;and

c. said biasing means includes a helical compression spring and means toadjust the voltage drop required to actuate said electromagnetic valvemeans.

11. A system as set forth in claim 10 wherein said ignition elementincludes variable resistance means electrically in series with saidvalve means.

12. A system as set forth in claim 11 wherein said igtance meanselectrically in series with said thermal nition element is a negativeslope thermistor.

valve and electrically in parallel with said electromagnetic valvemeans.

6. A direct ignition system as set forth in claim 5 wherein saidignition element is a negative slope thermistor.

13. A system as set forth in claim 10 wherein said adjustment meansincludes an adjustable threaded member providing a seat for said spring,said threaded member being oppositely disposed from said armature.

1. A direct ignition system for a valve controlled fuel burner comprising: a. an electrically actuated thermal valve connected between said fuel burner and a fuel supply; b. electromagnetic valve means fluidically in series with said thermal valve, said valve means having an armature and including means for biasing said armature in a normally closed position, said biasing means preventing actuation of said valve means at less than a minimum voltage drop across said valve means; c. means providing a fuel ignition element proximate to the outlet of said burner, said fuel ignition element reaching fuel ignition temperature in response to a predetermined current flow therethrough; and d. parallel electric circuit means operating i. said thermal valve in response to a fuel ignition temperature being present in said fuel ignition element, and ii. said electromagnetic valve means.
 2. A direct ignition system as set forth in claim 1 wherein said electromagnetic valve means is a solenoid valve and said biasing means includes a helical compression spring.
 3. A direct ignition system as set forth in claim 2 wherein said biasing means includes means to adjust the voltage drop required to actuate said valve means.
 4. A direct ignition system as set forth in claim 3 wherein said adjustment means includes an adjustable threaded member providing a seat for said spring, said threaded member being oppositely disposed from said armature.
 5. A direct ignition system as set forth in claim 1 wherein said fuel ignition element is a variable resistance means electrically in series with said thermal valve and electrically in parallel with said electromagnetiC valve means.
 6. A direct ignition system as set forth in claim 5 wherein said ignition element is a negative slope thermistor.
 7. A direct ignition system as set forth in claim 1 including: an electrical power source; and a manual switch series connected to said parallel circuit means to control the connection of said electrical power source to said parallel circuit means and said fuel ignition element.
 8. A direct ignition system as set forth in claim 1 wherein said fuel ignition element includes a negative resistance thermistor having a fuel ignition temperature when a predetermined current flows therethrough.
 9. A direct ignition system as set forth in claim 1 wherein said parallel circuit means includes a substantially constant resistance heater mounted to said thermal valve to control the opening of said thermal valve in response to said predetermined current flowing through said resistance heater.
 10. A system for igniting a fuel burner comprising: a. electromagnetic valve means connected between said fuel burner and a fuel supply, said valve means including an armature selectively movable between a position opening said valve means and a position closing said valve means, said valve means further including means for biasing said armature to prevent opening of said valve means at less than a minimum voltage drop across said valve means; b. means providing a fuel ignition element proximate to the outlet of said burner, said fuel ignition element reaching fuel ignition temperature in response to a predetermined current flow therethrough; and c. said biasing means includes a helical compression spring and means to adjust the voltage drop required to actuate said electromagnetic valve means.
 11. A system as set forth in claim 10 wherein said ignition element includes variable resistance means electrically in series with said valve means.
 12. A system as set forth in claim 11 wherein said ignition element is a negative slope thermistor.
 13. A system as set forth in claim 10 wherein said adjustment means includes an adjustable threaded member providing a seat for said spring, said threaded member being oppositely disposed from said armature. 